1. Field of the Invention
The present invention relates generally to composite materials and more particularly to composite materials having thermal conductive properties.
2. Related Art
Most electronic devices have enclosures such as boxes that cover and protect the electronic circuitry of the device. Unfortunately, these boxes also trap thermal energy or heat generated by the electronic circuitry during operation of the device. This heat can damage the electronic devices if allowed to build up within the box or housing. Consequently, many boxes for electronic devices are made from thermally conductive materials such as aluminum or other conductive metals. These thermally conductive enclosures allow the heat from the electronic device to dissipate by conduction before the heat builds to a critical temperature.
While metal boxes satisfy the thermal conductivity and strength requirements for housing electronic devices, they often add undesirable weight to the device. This weight can limit the usefulness of the device in some applications. For example, aircraft have many electronic devices that are enclosed in metal thermally conductive boxes. Unfortunately, metal boxes can add significant weight to the aircraft. It will be appreciated that the heavier an aircraft is, the more fuel required to lift the aircraft. Thus, the weight of the boxes can reduce the ability of the aircraft to carry additional cargo, or require additional fuel for the aircraft to fly.
One common alternative to heavier metallic components is to use lighter weight composite materials such as carbon fiber reinforced plastic, carbon composites, and the like. Such composite materials usually consist of fiber reinforcements, such as a carbon or graphite fibers, that are infused with a polymeric resin matrix, such as a phenolic resin, a polyimide resin, and the like.
These composite materials are attractive for many applications because they have relatively low weight and high strength properties which are desirable characteristics for structural components such as electronic enclosures. Unfortunately, while some carbon composite materials have been developed that have high thermal conductivity, and high ablative recession properties, these materials also lose strength in elevated temperature environments or can become brittle from repeated heating over time which can result in thermal stress cracking problems. Thus, use of these materials in forming electronic device enclosures has not been practical.